Historically, there was a need to be able to “pass” documents around the Internet and have them retain their layout exactly as the author intended. Adobe developed in the early 1990s a formatting language called PDF (portable document format) that allowed authors to do just that.
The key to the success of this format was to have the recipient be able to view the document without a lot of hassle. So, while the software that allowed the author to build PDF files was quite costly, the “reader” software was free and available to anyone off the Internet.
Before the pdf reader, people would send Microsoft Word documents if they wanted to do something fancy. Unfortunately, that required the recipient to have Microsoft Word installed on their computer to read it. Also, if the exact font was not used, then the recipient computer would substitute a different font and the layout would get all messed up. This is still a problem when sending Word documents.
Microsoft has a free Viewer that you can download from their site which does allow you to view but not change Word documents. There is a security hazard with Word (and the other Office applications) due to the fact that they can have embedded macros. These macros are small powerful programs that can do almost anything on the computer and have been the source of viruses entering computers. So, if you have the option, always send PDF files instead of a Word document as it is safer.
Adobe reader software has become such a standard, that many computer manufacturers bundle it with their new machines. The PDF format has become the method for creating owners manuals, government documents and instructional documents. Not to leave a good thing alone, Adobe has constantly embellished the standard that now it can accept data entry, play audio and video, and allow linkages to Internet sites. This added functionality has taken its toll on performance and size. What was a nimble little butterfly has now turned into a B-57 bomber. All those added capabilities have made Adobe Reader a prime target for the security hackers to attack.
Once thought indestructible, Adobe now has to update the product quite regularly against new and vicious security attacks that can cripple innocent users’ computers. Boo-hoo! So when Adobe wants to popup a message and update its reader, let its will be done.